The technical and patent literature contains many references to the inclusion of a nonmetallic ceramic component in a metal matrix and often the several phase structure is termed a composite material. U.S. Pat. No. 4,103,063 describes the formation of a ceramic-metallic eutectic structural material which is solidified from the melt and possesses oxidation resistant constituents. British Pat. No. 1,505,874 describes the fabrication of an electrically conductive composite material for use in high current electrical contacts. The contacts consist of silver with cadmium oxide and up to 2000 ppm potassium compounds. The oxide serves to help break the arc formed when contact is made and the cadium and potassium vapors serve to reduce the electron energy in the short duration arc.
Nickel-alumina cermets where fabricated by P. D. Djali and K. R. Linger (Proc. British Ceram. Soc., July 26, 1978, pp. 113-127) by hot-pressing alumina powder precoated with nickel to promote bonding between the particles. Near theoretical dense compacts were obtained with average mechanical properties. In similar work, C. S. Morgan used in situ deposition of metal coatings (Thin Solid Films, 39, December 1976, pp. 305-311) to coat ceramic powders and promote the wetting of the ceramic component. Using this approach, an Eu.sub.2 O.sub.3 powder was coated with W and hot-pressed to form a composite with improved thermal conductivity and improved thermal shock resistance for possible neutron absorbers for reactor use.
In yet another method to promote bonding between ceramic and metal powders, A. C. D. Chaklader and M. N. Shetty formed ceramic-metal composites by reactive hot pressing (Trans. Metal. Soc. Of AIME, 33, July 1965, pp. 1440-42). In their work, a monohydrate of Al.sub.2 O.sub.3 (Boehmite) was mixed with several metal powders and the "enhanced" reactivity of the Al.sub.2 O.sub.3 during decomposition used to promote interparticle bonding. A. V. Virkau and D. L. Johnson studied the fracture behavior of ZrO.sub.2 --Zr composites (J. Am. Cer. Soc., 60, Jan-Feb 1977, pp. 514-19) fabricated by hot-pressing pure ZrO.sub.2 and Zr powders in graphite dies at 1600.degree. C. Crack propagation was studied, as influenced by the residual stresses retained in these composites. Alternate methods of forming composites were reported by J. A. Alexander in the article entitled, "Five Ways to Fabricate Metal Matrix Composite Parts, (Materials Engineering, 68, July 1968, pp. 58-63). All of these composites contained filaments (i.e., boron or silicon carbide) and the metal was incorporated by methods ranging from liquid metal infiltration to powder metallurgy techniques.
In the only known reference where previously prepared metal oxide-metal eutectic materials were crushed and recemented together, N. Clausing (J. Am. Cer. Soc., 56, Aug. 1973, p. 197) hot-pressed Gd.sub.2 O.sub.3 --Mo and (Cr,Al).sub.2 O.sub.3 --Cr composite fragments to form mechanical test specimens. The work-of-fracture of these materials was significantly increased because of the ductile nature of the metallic fibers.
From this extensive background review, the present electrode material is unique simply because no previous effort has been made to form an electrode from this choice of starting materials (i.e., metal oxide-metal composite fragments and pure metallic powders).